Chaturmas means the four months of the monsoon, during which ascetics stay in one place. Staying in one place during the monsoon reduces the risk of causing accidental death to numerous insects and smaller forms of life that thrive during the rains.
During this period, it is a suitable time for lay Jains to have an annual renewal of the faith by listening to teachings of the Dharma and through meditation and vartas (self-control).
Read more about this topic: Jain Monasticism